Gauge hatch with liquid seal

ABSTRACT

A gauge hatch is provided that has a cover structure that incorporates a pallet/diaphragm combination and that is cooperatively associated with a pressure responsive liquid seal subassembly. The gauge hatch also incorporates a vent neck and a radially adjacent wall that defines with the vent neck a circumferentially extending reservoir. An exterior preferably radially extending arm permits the cover structure to be opened and inclined at an angle relative to the vent neck. Optionally, the cover may be kept in a closed position. The diaphragm normally seats upon the vent neck. A sealing liquid in the reservoir has a closed chamber over the reservoir liquid. When the arm is not held in a cover closed position, and up until a set vent neck pressure is reached, the liquid seal subassembly eliminates low level fugitive vapor emissions escaping from the diaphragm/seat region. The liquid seal subassembly opens when (a) a pressure in the vent neck occurs which exceeds the predetermined set point opening pressure of the cover structure; (b) a pressure in the closed chamber exceeds the predeterminable maximum liquid seal pressure, or (c) the cover structure is manually opened.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. Ser. No. 08/979,570, filed Nov.26, 1997, now U.S. Pat. No. 6,244,457 which in turn is acontinuation-in-part of co-pending U.S. Ser. No. 08/968,609, filed Nov.13, 1997, now U.S. Pat. No. 6,056,005, issued May 2, 2000.

FIELD OF THE INVENTION

This invention relates to gauge hatches which reduce low level fugitivevapor emissions prior to opening.

BACKGROUND OF THE INVENTION

At least one opening or vent is commonly provided in a tank (such as areactor, a processing device, a storage tank, a gas holder or othervessel) for the discharge, or the release, of an undesirably largepressure differential relative to the adjacent environment. To regulateuse or operation of the tank, avoid material loss from the tank, preventdamage to the tank, and/or minimize or even prevent environmentalcontamination with material from the tank, such a vent is commonlyprovided with a vent closure that can open at a preset pressuredifferential.

While various vent closure structures are known, one particularlyeffective structure utilizes a combination of pallet and diaphragm. Thepallet in normal valve operation extends across and closes the ventmouth while the associated diaphragm seats about and seals the ventmouth. The pallet and diaphragm combination can be considered tocomprise or to be included in a vent closure cover subassembly.

One commonly used type of vent closure structure that incorporates apallet and diaphragm combination is a gauge hatch. Characteristically, aconventional gauge hatch has a radially extending pivot arm that isassociated with an exterior central portion of the closure coversubassembly and that is pivotably associated with an exteriorcover-adjacent hitching or pivot post. Thus, this pivot arm permits thenormally closed cover subassembly to be pivoted to a vent open positionwhere the cover assembly and pivot arm do not interfere with tankinterior access for tank measurements that are made through a vent by anoperator. The cover subassembly in a gauge hatch thus can be assembledso as to be either opened manually by the operator, or openedautomatically if the associated tank reaches a set pressure wherepressure in the tank needs to be relieved.

Various means are known for regulating the opening or set pressure in agauge hatch-equipped vent where, at vent opening, the pallet anddiaphragm combination separate from the valve mouth. For example, oneparticularly effective pressure regulating means comprises a weight thatis inherently associated with, or that is effectively loaded onto theupper outside surface of the cover. Thus, in such an arrangement, theweight-loaded pallet and diaphragm combination of a cover separates fromits associated seated configuration at a preset tank pressure (which canbe super-atmospheric), thereby to achieve vent closure opening.

Some gauge hatches are provided with retainer means for optionallyholding the closure cover subassembly in a “bolted down” or equivalentvent closed configuration. The use of the retainer means can be anoperator-selected option. Such a gauge hatch is typically utilized forassociation with a tank that is also equipped with a vent valve whichautomatically opens when the associated tank reaches a set pressure.

One problem with such a pallet and diaphragm-type gauge hatch is that asmall volume of fugitive vapor emissions (typically parts per million)may occur between the diaphragm and its seat before either the setopening pressure of the gauge hatch cover is reached or the gauge hatchcover is manually opened by an operator.

The present invention overcomes this fugitive emissions problem forpallet and diaphragm type gauge hatch vent closures by incorporatinginto the gauge hatch structure a cooperating liquid seal. The liquidseal can function to virtually eliminate the escape of all fugitivevapor emissions prior to the opening of the pallet and diaphragmcombination either at a set opening pressure or at manual opening.

SUMMARY OF THE INVENTION

More particularly, this invention relates to a gauge hatch structure fora tank vent or the like comprising an integrated combination of (a) anormally pressure responsive vent closure cover means that incorporatesa pallet means with (b) a pressure-responsive liquid seal.

The inventive gauge hatch structure incorporates a cover subassembly, acooperating vent neck and wall means that along with the neck define areservoir. In the cover subassembly, the pallet means normally closesthe neck upper end. Preferably the pallet means in the cover assembly isalso associated with a diaphragm that is normally seated at the ventneck upper end portion. A flange-type mounting means for associating thegauge hatch with a tank or the like is also incorporated. Depending uponthe arrangement of the components employed in a particular embodiment ofthe gauge hatch structure, the inventive gauge hatch structure can beused either for relief of pressure in a tank holding super-atmosphericpressures, or as a manually operable vent port for use in tankmeasurements or the like. (The term “manually” or equivalent is used ina generic sense to indicate operation by a user or operator using a handor a foot.)

The gauge hatch cover subassembly and the liquid seal subassemblyoperate cooperatively. The combination functions so that the liquid sealsubassembly can eliminate the escape into the environment of low levelfugitive vapor emissions past the pallet and also the diaphragm seat (ifpresent) prior to the gauge valve cover subassembly opening either at aset pressure or manually.

In addition, the inventive gauge hatch structure includes an arm meansthat preferably radially extends across at least a portion of theclosure cover. A proximal portion of this arm means is preferablylocated at a central outside top portion of the cover means andfastening means interconnects these respective portions. A distalportion of this arm means is preferably located along the outsideperimeter of the cover means where pivotal connecting means is provided.Thus, in the vent open configuration, the cover means can be pivotedupwardly and away from the vent neck upper end portion so as to begenerally and preferably inclined relative thereto.

The arm means, the fastening means and the pivotal connecting means canhave various structures. For example, the arm means can include anoptional extension that extends from the cover central portion to anopposite side position (relative to the distal pivotal portion). Inaddition, retainer means can optionally be provided foroperator-selected usage in holding the gauge valve cover means in aclosed position with the pallet and the diaphragm (if present) seatedand sealed upon the vent neck upper end portion.

Either the inherent weight of the closure cover means, or the effectiveauxiliary equivalent weight exteriorly applied to the closure covermeans in combination with the inherent weight of the closure covermeans, determines the set point opening pressure of the cover means evenwhen the retainer means is present but is not operative or functional.

To facilitate manual opening and closing of the cover means, the armmeans can include, if desired, auxiliary member means, such as anupstanding foot treadle or the like, to facilitate the manual openingand closing of the cover means by an operator.

In the inventive gauge hatch, the liquid seal subassembly includes asealing liquid reservoir with a normally closed chamber that is locatedover a portion of the surface of a sealing liquid in the reservoir andthat is radially adjacent to the vent neck. A side wall region of theclosed chamber is defined by a baffle or apron that circumferentiallyextends around the vent neck and that is suspended preferably verticallyfrom the pallet means. The apron extends down into the reservoir and hasa lower end region that normally terminates below the surface of thesealing liquid in the reservoir.

When the inventive gauge hatch structure is adapted for use with a tankholding super atmospheric pressures, the reservoir is preferablycircumferentially positioned about the outside of the vent neck, and anysmall volume of fugitive vapor emissions that leaks past the contactseal existing at the normally closed seat between the vent neck and thepallet (and, if present, also the diaphragm) enters the closed chamber.The liquid seal between the reservoir liquid and the apron lower endregion does not allow vapor emissions that enter the closed chamber toescape and reach the atmosphere (that is, the environment).

The opening of the pallet and associated diaphragm at a set pointpressure is independent in operation from the opening of the liquidseal. If and when the leakage of fugitive vapor emissions increases(perhaps caused by tank pressure increase), the pressure in the closedchamber increases. The increase causes the reservoir liquid in theclosed chamber to be displaced downwardly and to move into an adjacentreservoir region, but the seal is maintained. Eventually the pressurecan increase to a level which is in excess of the maximum displacableliquid head in the closed chamber. This level defines the maximum liquidseal pressure of the closed chamber.

In the inventive gauge hatch structure, the cover means preferablyincorporates a combination of diaphragm and associated pallet. The covermeans preferably lifts (that is, opens and separates) from theneck-associated seating surface at a set point pressure which ispreferably at or below the maximum liquid seal holding pressure.Preferably, the inventive gauge hatch structure is leak-free until thecover means lifts from the seat at the neck either at a set point ormanually.

The inventive gauge hatch structure can optionally be associated withvarious auxiliary subassemblies, such as a constant level sealing liquidsupply source, and/or a signaling device (which preferably can beremotely sensed).

The set pressure opening of the cover subassembly is based upon the tankpressures applied to the cover structure. When such opening occurs, theapron is separated from the reservoir sealing liquid and tank pressureis vented to the atmosphere.

Various features of the inventive gauge hatch structure are discussedand disclosed in the following description.

Other features, objects, advantages, aims, embodiments, applications andthe like will be apparent to those skilled in the art from the presentdescription taken with the accompanying drawings and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is an axial and diametrical cross-sectional view taken throughone embodiment of a gauge hatch structure of the invention that isadapted for use at superatmospheric pressure;

FIG. 2 is a top plan view of the FIG. 1 gauge hatch;

FIG. 3 is a fragmentary view similar to a portion 1 of FIG. 1, butshowing an alternative embodiment of a gauge hatch structure of theinvention;

FIG. 4 is a fragmentary perspective view of the embodiment of FIG. 3;

FIG. 5 is a fragmentary view similar to a portion of FIG. 1, but showinga further alternative embodiment of a gauge hatch structure of theinvention;

FIG. 6 is a fragmentary view similar to a portion of FIG. 1, but showinga further alternative embodiment of a gauge hatch structure of theinvention;

FIG. 7 is a view similar to FIG. 1, but showing a further alternativeembodiment of a gauge hatch structure of the invention;

FIG. 8 is a fragmentary view similar to a portion of FIG. 7, but showingan alternative embodiment of a gauge hatch structure of the invention;

FIG. 9 is a view similar to FIG. 1, but showing an alternativeembodiment of a gauge hatch structure of the invention that is inassociation with a (fragmentarily shown) tank;

FIG. 10 is a top plan view of the FIG. 9 gauge hatch;

FIG. 11 is a view similar to FIG. 1, but showing an alterativeembodiment of a gauge hatch structure of the invention;

FIG. 12 is a top plan view of the FIG. 11 gauge hatch;

FIG. 13 is a view similar to FIG. 1, but showing an alternativeembodiment of a gauge hatch structure of the invention;

FIG. 14 is a top plan view of the FIG. 13 gauge hatch; and

FIG. 15 is an enlarged fragmentary view similar to FIG. 1 showing thediaphragm in cross-section.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, an embodiment 20 of a pressure responsivegauge hatch structure of the present invention is shown. A gauge hatchstructure 20 is adapted for use with a tank operating atsuperatmospheric pressures. The gauge hatch structure 20 incorporates aneck 21 that is cooperatively associated by welding or the like at itsinner end with a flattened but toroidally configured base plate 22. Theperimetrically outer upper edge of the base plate 22 is associated bywelding or the like with an upstanding sleeve 23. The neck 21 and thesleeve 23 are cross-sectionally circular and are coaxially arrangedrelative to one another.

Radially outwardly extending from the circumference of the base plate 22is a flattened support flange 24. The support flange 24 generallyextends here radially outwardly from base plate 22 and the sleeve 23.Upstanding in opposed relationship to each other upon opposite sides ofthe support flange 24 are two pairs of upstanding ears 26 and 27,respectively (see FIG. 2). These ears 26 and 27 are convenientlyattached to the support flange 24 by welding or the like. The neck 21,the base plate 22, the sleeve 23 cooperate to define a sealing liquidreservoir 28 that extends circumferentially around the neck 21. Thereservoir 28 has an open end that generally radially extends adjacentlyto upper end portion of the neck 21.

The gauge hatch 20 has a cover 29 that incorporates among othercomponents a pallet plate 31. Adjacent to the periphery of the bottomsurface of the pallet plate 31 is an upraised circumferential channelwhich preferably receives therein a diaphragm 32. Particularly withclose tolerances, the diaphragm can be absent. The pallet plate 31supports and is associated with the diaphragm 32. The diaphragm 32 isadapted here to matingly seat over the outer upper end of the neck 21 sothat a seating and generally sealed interrelationship is achievedbetween the diaphragm 32 and the outer end. Conveniently, the outerupper end of the neck 21 is machined so as to provide a uniform,circumferentially extending seating surface. Over the upper face of thepallet plate 31, a top plate 33 is provided in cover 29. The top plate33 has a larger diameter than the pallet plate 31. The top plate 33extends radially beyond the outer perimeter of the pallet plate 31 so asto generally overlie and shield but not seal the upper circumferentiallyextending edge portions of the sleeve 23.

An apron 34 circumferentially and downwardly extends from the top plate33. The apron 34 is joined to the top plate 33 by welding or the like.The apron 34 is located in radially adjacent relationship to the neck21. The apron 34 extends through the open end of the reservoir 28 anddown into the reservoir 28, and the apron 34 has a lower end 51.Preferably, the lower end 51 of the apron 24 is in longitudinallyupwardly spaced relationship relative to the inside surface of thereservoir 28 (here defined by the base plate 22). The pallet plate 31and the top plate 33 can be considered to comprise a pallet platesubassembly 31/33. Those skilled in the art will appreciate that areservoir 28 can be defined by various means and arrangements.

The gauge hatch structure 20 incorporates an arm 36 which, as shown,preferably radially extends here from a central outer location on cover29 to a position between the ears 26. The inner end, the arm 36 overcover 29 is here designated as the proximal portion 37 and the outer endof the arm 36 at ears 26 is here designated as the distal portion 38.The proximal portion 37 on its bottom face is provided with a blindchannel 39. The arm 36 is conveniently comprised of a molded metal toavoid heat shrinkage during molding, the arm 36 is provided with a pairof elongated depressions 35, each one in opposed relationship to theother, that extend in opposite sides of the arm 36.

Extending axially through the pallet plate assembly 31/33 is an aperturewhich is provided with a nut and bolt assembly 41. The head of the boltof the nut and bolt assembly 41 is cylindrical and adapted to bereceived in the blind channel 39. Perpendicularly relative to the blindchannel 39, an aperture is formed in the proximal portion 37 and amating aperture is provided in the head of the nut and bolt assembly 41.Thus, a pivot pin 42 can be extended therethrough when these aperturesare aligned, thereby to hold the head of the nut and bolt assembly 41 inassociation with the proximal portion 37 preferably in a generally looseconnection so that some play is preferably afforded between the cover 29and the arm 36 proximal portion 37. Such play permits the cover assembly29 to be readily self-seating relative to the upper end of the neck 21so that the diaphragm 32 seats easily by itself on the upper end of theneck 21 under the inherent weight of the cover assembly 29.

The distal portion 38 of the arm 36 is pivotally interconnected betweenthe ears 26 by means of a pivot pin 43 that extends through alignedchannels that are defined in the ears 26 and in the distal portion 38.Conveniently and preferably, the pivot pin 43 is here headed at one endand provided with a locking cotter pin 44 at its opposite end, althoughother alternative means for mounting a pivot pin can be employed, ifdesired.

As an auxiliary means to aid in the manual opening of the cover 29relative to the neck 21, thereby unseating the diaphragm 32 from theupper end of the neck 21, the arm 36 is provided with an upstandingserrated treadle 46 at its distal portion 38. Preferably, the treadle 46is unitarily formed with the distal portion 37. The treadle 46 isadapted to be engaged by a foot shoe sole or heel portion (as worn by anoperator). Thus, an operator can open the cover 29 by placing his footshoe sole (not shown) on the treadle 46. When open to its maximumextent, the cover 29 and the arm 36 preferably has the generalconfiguration illustrated in phantom in FIG. 1.

It is presently preferred to have the maximum open inclination angle forthe arm 36 and cover 29 fall in the range of about 75° to about 80° forpurposes of permitting inspection and easy entry to an associated tankor the like for gauging, sampling, measurement or the like, yetpermitting the cover 29 to close by itself when released. Such aninclination angle is preferably achieved by inserting a stop pin 47through aligned apertures defined in the ears 26. The location of thestop pin 47 is such that the treadle 46 or the distal portion 38 isengaged therewith when the arm 36 and cover 29 have reached a desiredmaximum inclination angle. Removing the foot causes the cover 29 toclose in a self-seating and self-closing manner to achieve a closedconfiguration as illustrated in FIG. 1.

Except for the diaphragm 32, components of the gauge hatch structure 20are preferably formed of metal (preliminarily cast and then machined totolerances). A presently convenient metal is an aluminum alloy. Thediaphragm 32 can be variously comprised, but a preferred material ofconstruction is polytetrafluoroethylene. Diaphragm 32 preferably has aflattened disclike configuration.

The interrelationship between the neck 21 and the cover 29 is such thatthe cover 29 including all of its associated components can be pivotedupwardly and away from the upper end of the neck 21 when the gas (orvapor) pressure inside the neck 21 exceeds a point pressure thatcorresponds to the total effective weight upon the cover 29 on the neck21. If desired, the cover assembly 29 weight can be augmented bypositioning weights on the upper outside surface of the cover 29 (notshown).The tilt angle of the cover 29 when opened by gas pressure insidethe neck 21, as those skilled in the art will appreciate, is roughlyproportional to the pressure existing in the neck 21. Such pressure isusually not sufficient to elevate the cover 29 to its fully extendedposition (such as illustrated in FIG. 1 in phantom).

In use, the reservoir 28 is conveniently partially filled manually witha sealing liquid, such as a petroleum hydrocarbon or the like. The apron34 divides the reservoir 28 into approximately two chambers as shown inFIG. 1 identified as an inner chamber 48 that is radially adjacent tocircumferential outer surface portions of the neck 21, and an outerchamber 49 that is radially located between the apron 34 and the sleeve23. The volume of the outer chamber 49 is at least equal to andpreferably is greater than the volume of the inner chamber 48. Thetypical radial distance between the neck 21 and the apron 34 is lessthan or equal to (but not greater than) the typical radial distancebetween the apron 34 and the sleeve 23. The apron 34 has a preferablyuniform lower edge or terminus 51 that is located in upwardly preferablyuniformly spaced relationship to the inside upper service of the baseplate 22. The level of sealing liquid 52 in the reservoir 28 is at leastsufficient to immerse the lower edge 51 of the apron 34 therein, asillustrated in FIG. 1, for example.

When the cover 29 closes the mouth of neck 21 so that the pallet 32extends over the upper end of the neck 21 and the diaphragm 32 is seatedat the upper end portion of the neck 21, any small volume of fugitivevapor emissions passing from the interior of neck 21 through the sealdefined by the seating area existing between the diaphragm 32 and theouter end of the neck 21 is directed into the closed chamber 48 existingabove the level of the sealing liquid 52 in the inner chamber 48. Inthis condition, the inner chamber 48 is defined by the sealing liquid52, the neck 21, the pallet plate subassembly 31/33, the diaphragm 32and the apron 34. A liquid seal existing between the sealing liquid 52and apron 51 above the lower edge 51 does not allow vapor emissionspassing the seal between the diaphragm 32 and the outer end of the neck21 to reach the atmosphere. Initially, the level of the sealing liquid52 in the closed chamber 48 is initially the same as the level of thesealing liquid in the outer chamber 49, but, because of the aboveindicated chamber 48 and chamber 49 size differences, the normal volumeof the sealing liquid 52 in the closed chamber 48 is usually less thanthe normal open volume existing over the sealing liquid 52 in the outerchamber 49. In this condition, the inner chamber 48 is defined by thesealing liquid 52, the neck 21, the pallet plate subassembly 31/33, thediaphragm 32 and the apron 34. A liquid seal existing between thesealing liquid 52 and apron 51 above the lower edge 51 does not allowvapor emissions passing the seal between the diaphragm 32 and the outerend of the neck 21 to reach the atmosphere. Initially, the level of thesealing liquid 52 in the closed chamber 48 is initially the same as thelevel of the sealing liquid in the outer chamber 49, but, because of theabove indicated chamber 48 and chamber 49 size differences, the normalvolume of the sealing liquid 52 in the closed chamber 48 is usually lessthan the normal open volume existing over the sealing liquid 52 in theouter chamber 49.

When and if the vapor pressure in the interior of the neck 21 increases,so that the amount of vapor emissions passing through the seal betweenthe diaphragm 32 and the outer end of the neck 21 increases, thepressure in the volume of vapor in the chamber 48 above the level of thesealing liquid 52 increases. The pressure increase resultingly displacesthe liquid 52 downwards in the chamber 38 into the open and radiallyadjacent outer reservoir region or chamber 49, but the liquid sealexisting between the lower edge 51 of the apron 34 and the liquid 52 isstill maintained. The outer chamber 49 is thus defined in the reservoir28 to be radially adjacent to the normally closed interior 48. As in thechamber 48, the open volume above the sealing liquid 52 in the chamber49 is defined by the level of sealing liquid 52 therein. The chamber 49is defined by the adjacent wall portions of the apron 34 and sleeve 23.The top of the outer chamber 49 is open, as indicated above, and theouter chamber 49 has a total volume that is preferably greater than thetotal volume of the chamber 48.

When and if the vapor pressure in the neck 21 and in the chamber 48reaches a level where the sealing liquid 52 level in the interiorchamber 48 effectively becomes less than the lower edge 51 of the apron34, then the maximum liquid seal pressure of the gauge hatch structure20 is exceeded and the liquid seal is opened. At this condition, vaporin the chamber 48 is vented to the atmosphere from the chamber 48through the chamber 49 and out through the top open area of the outerchamber 49. By controlling the density of the sealing liquid and thefill level of the sealing liquid in the reservoir, the maximum liquidseal pressure for a particular sealing liquid 53 and a particular gaugehatch structure 20 can be selected or rated.

Preferably, the opening pressure (that, is the unseating pressure) ofthe diaphragm 32 from the upper end of neck 21 is selected so as to beat or below the maximum liquid seal pressure. Other opening pressurescan be utilized if desired. For example, assume that the cover 29 eitherby itself or with added effective weight provides a settingcorresponding to two inches of water column, and that the liquid sealexisting between the liquid 52 and the apron 34 down to the lower edge51 is set to provide a maximum liquid column equivalent to four incheswater column. As the tank associated with the inside of the neck 21increases in pressure, so that the vapor leakage pressure into theclosed chamber 48 increases, the sealing liquid 52 in reservoir 28 isdisplaced (as described above). However, the closed chamber 48 stillcontains any small volume vapor leakage from the neck 21 that passes theseat at the outer end of the neck 21 with the diaphragm 32. When thepressure reaches the equivalent in the neck 21 of two inches watercolumn, then the weighted cover 29 lifts the diaphragm 32 and the liquidseal valve opens and the desired pressure relief for the associated tankthrough the neck 21 is achieved. The gauge hatch structure 20 is leakfree until the diaphragm 32 lifts. After pressure venting or pressurerelease is accomplished, the cover 29 closes and reseats itself on theneck 21 upper end.

Those skilled in the art.will appreciate that various alternativearrangements for the gauge hatch structure 20 can be provided. For oneexample, as shown in FIG. 5, arm 36 can be rigidly fixed to the cover 29and can be loosely associated with pivot pin 43, as illustrated in FIG.5 so that the preferred small relative movement between the cover 29 andthe ears 26 is achieved by loose journaling of the pivot pin 43.

A somewhat similar alternative arrangement to that shown in FIG. 5, isillustrated in FIG. 6 where the arm 36 is shortened and rigidlyconnected to a perimeter-adjacent top portion of the cover 29. Thus, inboth the FIG. 5 and FIG. 6 arrangements, the preferred self-adjustingand self-seating feature for the cover 29 is achieved through theconnection of the arm 36 with the ears 26.

A further alternative arrangement is illustrated in FIGS. 3 and 4. Here,in place of weights being added to the upper top surface of the apron34, the set pressure is determined by the effective weight provided by asheer pin 53 that is reversibly and manually insertable throughrespective aligned apertures in the distal portion 38 and the ears 26.In this arrangement, the cover 29 opens when a predetermined maximumpressure in the neck 21 is reached that is sufficient to overcome theeffective inherent weight of the cover 29 plus the force needed to sheerthe sheer pin 53.

Two further alternative arrangements are illustrated in FIG. 7 and FIG.8, respectively. There, to avoid the need for a plurality of separatelyand individually made weldments such as are employed in the gauge hatchstructure 20, precast bodies are employed that are arranged to reduce oreliminate weldments. Thus, in each of the arrangements of FIG. 7 andFIG. 8, the cover 29 and the arm 36 are each integrated and comprised ofone molded subassembly while the reservoir 28, the neck 21, the sleeve23, the neck support or base plate 22 (shown in FIG. 7, not shown inFIG. 8), and the mounting flange 24 (shown in FIG. 7, not shown in FIG.8) are integrated and formed as a second unitarily molded subassembly.

Referring to FIGS. 9 and 10, there is seen another embodiment 65 of agauge hatch structure of the invention. Components of the gauge hatch 65that are similar to components of the gauge hatch structure 20 aresimilarly numbered, but with the addition of prime marks thereto foridentification purposes.

In the gauge hatch structure 65, the support flange 24′ and the sleeve23′ are integrally formed by casting or the like with the insideperimeter of the flange 24′ being adjacent to the upper end portion ofthe sleeve 23′ and with the circumferentially extending region of theflange 24′ that is adjacent to the inside perimeter thereof being slopeddownwardly. Such an arrangement permits the lower end portion of thesleeve 23′ to be restably received through and to extend about theperimeter of a vent aperture 66 in a tank 67 (shown fragmentarily) withthe upper end portion of the sleeve 23′ being raised relative to thevent aperture 66. Machine bolts 68 circumferentially spaced extendthrough the flange 24′ and mount the gauge hatch 65 to the tank 67.Sealing means (not shown) can be employed to sealingly engage the flange24′ with the tank 67.

The neck 21′ is supported in a concentric orientation relative to thesleeve 23′ by means of a flattened washer-shaped disc (or bottom plate)69. The disc 69 is mounted by welding or the like that extends aroundits outer perimeter to the lower inside end portion of the sleeve 23′and also around its inner perimeter adjacent to the lower outside endportion of the neck 21′. Thus, the desired reservoir 28′ is defined bythe sleeve 23′, the disc 69, and the neck 21′. Reservoir 28′ isconveniently manually charged with a sealing liquid 52′. Chamber sizerelationships are as above described in relation to gauge hatchstructure 20.

The apron 34′ is here conveniently formed as a circumferential flangeabout the periphery of a generally flat circular pallet plate 71. Plate71 is mounted coaxially in face to face engagement with the centralunder surface of a cover plate 72 which radially outwardly extendsbeyond the plate 71 to an extent sufficient to overlie protectively butnot sealingly the upper end portions of the sleeve 23′. The apron 34′extends down into the reservoir 28′ so that its lower end portion isimmersed in the liquid 52′.

The pallet plate 71 extends over the upper end of the neck 21′. Adjacentto the pallet plate 71 periphery and on the pallet plate 71 undersurface, there is preferably received and supported a diaphragm 32′ inan upwardly extending circumferential depression defined in plate 71.The pallet plate 71 is mounted coaxially in face-to-face engagement withthe central undersurface of the plate 72. The plate 71, and the coverplate 72 (together with the diaphragm 32′) are held in engagedrelationship by the nut and bolt assembly 41′, and the assembledarrangement can be considered to comprise a cover subassembly 29′. Thediaphragm 32′ is normally seated in a closed position upon the upper endportion of the neck 21′.

The operation and functioning of the gauge hatch 65 is similar to thatdescribed above for the gauge hatch 20.

Referring to FIGS. 11 and 12, there is seen another embodiment 75 of agauge hatch structure of the invention. Components of gauge hatch 75which correspond to components of the gauge hatch 20 are similarlynumbered but with the addition of prime marks thereto for identificationpurposes.

In gauge hatch 75, the lower end portion of the neck 21′ is joined bywelding or the like to the inside perimeter of the support flange 24′.The central aperture 76 in the flange 24′ is adapted to be centered overa tank vent 68 and flange 24′ is bolted thereto by machine bolts (notshown) or the like.

The vent neck 21′ is here associated with the circumferentially extendedmember 77 which is generally L-configured. The member 77 has a laterallyextending base leg 78 and an upstanding leg 79. The terminal end of thebase leg 78 is connected abuttingly (preferably by welding) tocircumferential outside portions of the vent neck 21′. The leg 78extends circumferentially about and in radially outwardly spacedrelationship to the vent neck 21′. The upstanding leg 79 extendscircumferentially and radially, and preferably in uniformly spacedrelationship, about portions of the vent neck 21′. Thus, the member 77and the vent neck 21′ cooperate to define a sealing liquid holdingreservoir 28′ that circumferentially extends about the outside of theneck 21′ and is in longitudinally preferably equally spaced but adjacentrelationship to the outer end of the neck 21′. Those skilled in the artwill readily appreciate that the member 77 can have variousconfigurations and that the reservoir 28′ can be defined by variousmeans and can have various sizes.

The gauge hatch structure 75 preferably includes a circumferentially andcontinuously extending diaphragm 32′ that is releasably seated over theouter end of the neck 21′ when the gauge hatch structure 75 is in itsnormal diaphragm 32′ closed and seated position (as shown in FIG. 11).

A hatch cover 81 is provided that supports and is associated with thediaphragm 32′. The hatch cover assembly 81 cooperates with the diaphragm32′ to provide a closure for the outer end 17 of the neck 21′. The cover81 normally closes the neck 21′ at its outer end. The cover 81 withdiaphragm 32′ extends diametrically across the outer end of neck 21′.Conveniently and preferably, the cover 81 is comprised of a cast metalbody that is centrally slightly upwardly dome configured. The cover 81has defined on its bottom surface in spaced but adjacent relationship toits periphery a circumferentially extending, upwardly displaceddepression within which the diaphragm 32′ is placed. The cover 81 has alarger diameter than the diameter of the neck 21′. Downwardly extendingfrom the outer perimeter of the cover 81 is a circumferentiallyextending apron 34′. The apron 34′ extends outside and preferablyvertically and longitudinally to the neck 21′, and preferably the apron34′ is located in radially uniformly spaced relationship between theneck 21′ and the upstanding leg 79 of member 77. When the hatch cover 81is in its normally closed position over the upper end of the neck 21′,the apron 34′ lower end portions are immersed in a sealing liquid thatis contained within the reservoir 28′.

The hatch cover 81 has an aperture axially extending therein which isprovided with a nut and bolt assembly 80 that threadably associates witha blind channel defined in a mounting post 82. The gauge hatch structure75 incorporates an arm 83 which, as shown, preferably diametricallyextends over and across the hatch cover 81. One outer end of the arm 83is here designated as the distal portion 84. The distal portion 84 ofthe arm 83 is pivotally interconnected between the ears 26′ by means ofa pivot pin 43′ that extends through aligned channels that are definedin the ears 26′ and in the distal portion 84. Conveniently andpreferably, the pivot pin 43′ is here headed at one end and providedwith a locking cotter pin 44′ at its opposite end, although otheralternative means for mounting a pivot pin can be employed, if desired.

As an auxiliary means to aid in the opening of the hatch cover 81relative to the neck 21′, thereby unseating the diaphragm 32′ from theupper end of the neck 21′, the arm 83 is provided at its distal end 84with an upstanding serrated treadle 46′. Preferably, the treadle 46′ isunitarily formed with the distal portion 84.

The central region of the arm 83 is provided on its bottom face with ablind channel 86. The mounting post 82 is adapted to the looselyreceived within the blind channel 86. A pivot pin 87 is adapted to beextended through aligned cross channels that are defined in each of themounting post 82 and the mid portion of the arm 83, the channelsextending generally perpendicularly to the arm 83. Thus, the pivot pin87 is preferably adapted to hold the mounting post 82 generally in aloose connection relative to the arm 83 so that some play is affordedbetween the cover 81 and the arm 83 thereby to permit the cover 81 to begenerally and easily self-seating relative to the upper end of neck 21′.The diaphragm 32′ then seats by itself on the upper end of the neck 21′under the inherent weight of the hatch cover assembly 81 when the cover81 is closed.

The end of the arm 83 that is opposed to the distal portion 84 is hereinidentified as the proximal portion 88 of arm 83. For purposes ofimproving the leverage action by the middle of the arm 83 against themid portion of the cover 81 and the mounting post 82, the length of thearm 83, between the mid portion and the proximal portion 88, is inclinedat its mid portion relative to the length of arm 83 between the mountingpost 82 and the distal portion 84. Between the ears 27′ is positioned aneyebolt 89 whose eye is pivotally mounted on a pivot pin 91 that extendsthrough aligned respective apertures in the ears 27′. The pivot pin 91can be structurally similar to the pivot pin 43′ and the pin 91 is hereillustratively associated with a cotter pin 92. The eyebolt 89 is thuspivotally movable from an upright location such as shown in FIG. 11 to adownwardly inclined location (not shown).

In its upright location, as shown in FIG. 11, the eyebolt is extendablethrough a vertical channel defined in the proximal portion 88 of the arm83, the proximal portion 88 preferably being oriented so as to extendperpendicularly relative to the eyebolt 89 when the eyebolt 89 is in theconnected upright position illustrated in FIG. 11. The upper outer endof the eyebolt 89 is preferably fitted with a washer 93 and isthreadably associated with a wing nut 94. With the proximal portion 88thus engaged with the eyebolt 89 and a wing bolt 94, the arm 83 isadapted to hold down the cover 81 so that cover 81 does not open, forexample, in response to elevated pressures existing in the neck 21′.

When the wing nut 94 is disassociated from the eyebolt 89 (with thewasher 93), the arm 83 can be pivoted upwardly about pivot 43′ by, forexample, the application of an operator's foot against the treadle 46′,thereby opening the cover 81. When pivoted open to its maximum extend,the cover 81, like the cover 29, has the general inclined configurationshown in phantom in FIG. 11. It is presently preferred to have themaximum open inclination angle for the arm 83 fall in the range of about75° to about 80° for purposes of permitting inspection and easy entryinto an associated tank or the like and for accomplishing gauging, orfor making sampling measurements, or the like. The inclination angle, asin the case of the gauge hatch structure 20, is achieved through the useof the stop pin 47′ as shown in FIG. 11. Removing the foot releases thecover 81 and causes it to close in a self-seating and self-aligningmanner, thereby to achieve the closed configuration illustrated in FIG.11.

Use of the eyebolt 89, the washer 93, and the wing nut 94 in combinationby an operator to bolt down the arm 83 is optional. When the combinationis not used, the cover 81 opens upwardly at a set pressure, dependingupon the effective weight of the cover, in a manner similar to thatabove described for the gauge hatch structure 20.

The operation of the gauge hatch structure 75 is similar to that of thegauge hatch structure 20.

Referring to FIGS. 13 and 14, there is seen another embodiment 98 of agauge hatch structure of this invention. Components of the gauge hatchstructure 98 which correspond to similar components in the gauge hatchstructure 20 and in the gauge hatch structure 75 are similarly numbered,but with the addition of prime marks thereto for identificationpurposes.

In the gauge hatch structure 98, the arm 83′ and the hatch cover 81′ arefabricated from steel plate stock. The arm 83′ extends straight exceptfor an upturned treadle 46′ at its distal portion 84′. The configurationof the cover 81′ and arm 83′ in their fully open configuration is shownin phantom fragmentarily. The arm 83′ includes a stop 102 at distalportion 84 which limits the upward tilt thereof.

The gauge hatch 98 includes a hook 99 for suspending a thermometer orthe like and an apertured bracket 100 for a similar function.

In the practice of this invention, it is now preferred in a coversubassembly for the diaphragm and the pallet to be so associated that agas (such as air) provide a cushion or space between the diaphragm andadjacent portions of the pallet. Thus, a modified diaphragm and palletstructure, such as shown in Lisciani U.S. Pat. No. 3,394,732 can beutilized.

As those of ordinary skill in the art will readily appreciate from theforegoing disclosures taken with the accompanying drawings, the presentinvention has a number of advantages and features.

In particular, the gauge hatch assemblies of this invention preventfugitive vapor emissions from escaping to the atmosphere prior to gaugehatch opening either at a set point pressure or manually.

A gauge hatch assembly of this invention provides two independentsealing points. The weight-loaded cover that incorporates the pallet andthe diaphragm determines the set point opening of the gauge hatch. Theliquid seal provides additional sealing up to its limiting pressure orvacuum set point opening.

The set point of a gauge hatch assembly of this invention can preferablybe varied by changing the actual or effective weight of its cover. Apresent preference is to select a set point for the cover that ranges upto the maximum liquid column pressure equivalent; however, for certainapplications, the liquid seal set point opening pressure can be selectedto be greater than the pallet/diaphragm opening pressure set point asthose skilled in the art will appreciate.

In a gauge hatch assembly of this invention, the liquid reservoir andthe cylindrical apron extension form the cover subassembly and are eachsized and configured so that the sealing liquid in a normally closedchamber associated with the reservoir is displaced by pressure but iscontained in the reservoir until a selected set maximum liquid pressureis achieved. In effect, relative to the valve neck, a radially outeropen chamber that is adjacent the normally closed chamber is defined inthe reservoir by the cylindrical apron. The outer chamber preferably hasa greater volume than the inner normally closed pressure chamber.

The primary gauge hatch seal that utilizes a diaphragm/palletcombination is independent of the liquid seal. If for any reason thereservoir is not charged with sealing liquid, or is inoperative, thenthe primary gauge hatch seal still function.

In a gauge hatch structure that is adapted for vacuum venting, thesealing liquid reservoir is preferably and conveniently isolated fromthe interior of the gauge hatch.structure by the primary gauge hatchseal that is provided by the pallet/diaphragm/neck seal. Then, if thereis a tendency to develop moisture on the inside the gauge hatch neck,the reservoir is not directly contacted with such moisture.

It will be understood that this invention can be embodied in otherspecific forms without departing from the spirit, scope and essentialcharacteristics thereof. The present teachings are illustrative and notrestrictive. The scope of the invention is indicated by the appendedclaims rather than by the preceding description.

What is claimed is:
 1. A gauge hatch structure comprising in combination: (a) a vent neck with opposed first and second end portions; (b) circumferentially extending wall members defining in combination with said vent neck a sealing liquid reservoir that extends circumferentially around said vent neck, said reservoir having an open end generally radially adjacent to said first end portion; (c) means for mounting said vent neck and said wall members and having.an outward portion that extends radially outwardly beyond the outermost one of said vent neck and said wall members; (d) a cover comprising (1) a diaphragm normally releasably seated about said first end portion, (2) a pallet plate sealingly supporting said diaphragm and extending across and closing said first end portion, and (3) an apron circumferentially and downwardly extending from a top plate covering said pallet plate and located in radially adjacent relationship to said vent neck and extending through said open end into said reservoir, said apron having a lower end; and (e) an arm structure having a proximal portion joined at an outside region of said cover and a distal portion up located adjacent said outward portion, said arm structure means including a pivotal mounting structure between said distal portion and said outward portion; whereby said cover can be pivoted upwardly and away from said first end portion about said distal portion to a maximum extent such that said cover is inclined relative to said first end portion and said diaphragm is unseated; whereby, when said reservoir is partially filled with a sealing liquid to a liquid level at least sufficient to immerse said lower end, a liquid sealed chamber is produced therein between said apron and said vent neck when said diaphragm is so seated; and whereby, when vapor emissions pass between said first end portion and said diaphragm when said diaphragm is so seated, said vapor emissions enter and are retained in said chamber until the first occurrence of one of the following events: (a) the pressure of said vapor emissions in said liquid sealed chamber is sufficient to displace in said reservoir said sealing liquid from said chamber and expose said lower end, thereby to release said vapor emissions from said chamber upwardly through said open end, (b) the pressure of said vapor emissions in said vent neck exceeds a set pressure that is determined by the weight of said cover plus any effective weight applied to said cover so that said diaphragm is unseated and said cover so pivoted upwardly, or (c) said cover is manually opened.
 2. The gauge hatch structure of claim 1 wherein said reservoir is so charged with said sealing liquid.
 3. The gauge hatch structure of claim 2 wherein the resulting said liquid level is sufficient to achieve a maximum liquid seal in said sealed chamber which is at least equal to said diaphragm unseating pressure.
 4. A method for regulating low level fugitive vapor emissions from a vent neck, said method comprising the steps of: (a) associating said vent neck with a pallet type of gauge hatch so that said, vent neck and the pallet of said gauge hatch cooperate to produce a seat zone that normally closes said vent neck; (b) associating with said pallet a weight which causes said pallet to unseat from said seat zone and thereby open said gauge hatch when a predetermined pressure occurs in said vent neck; and (c) locating a liquid reservoir circumferentially around said vent neck and positioning in the sealing liquid of said liquid reservoir the lower end portion of an apron that circumferentially extends around said vent neck and that downwardly extends from said pallet into said liquid so that a normally closed chamber exists between said apron and said vent neck when said seat zone exists until a predetermined vapor pressure occurs in said closed chamber; whereby all of said fugitive vapor emissions that escape past said seat zone when said seat zone exists are retained in said closed chamber until (a) said predetermined pressure is reached, (b) the pressure in said closed chamber becomes sufficient to expose said lower end portion, or (c) said pallet is manually opened.
 5. The method of claim 4 wherein said pallet is associated with a diaphragm.
 6. The method of claim 4 where said pallet is mechanically held in said vent neck closed position so that said fugitive vapor emissions are retained in said closed chamber until said pallet is manually opened.by release of said mechanical holding. 